Questions | Answer | Explanations |
11 Which compound contains both ionic and covalent
bonds?
(1) CaCO3 (3) MgF2
(2) PCl3 (4) CH2O | 1 | look for 3 elements and one must be a metal |
12 Which formula represents a nonpolar molecule?
(1) HCl (3) NH3
(2) H2O (4) CF4 | 4 | draw it. It is symmetrical |
13 When a lithium atom forms an Li+ ion, the lithium atom
(1) gains a proton
(2) gains an electron
(3) loses a proton
(4) loses an electron | 4 | becomes positive by losing an electron |
 | 2 | 3 valence electrons 2-3 |
15 A sample is prepared by completely dissolving 10.0 grams of NaCl in 1.0 liter of H2O. Which classification best describes this sample?
(1) homogeneous compound
(2) homogeneous mixture
(3) heterogeneous compound
(4) heterogeneous mixture | 2 | solutions are homogenous mixtures |
16 Which form of energy is converted to thermal energy when propane burns in air?
(1) electromagnetic (3) electrical
(2) nuclear (4) chemical | 4 | chemical comes from bonds |
17 Which physical changes are endothermic?
(1) melting and freezing
(2) melting and evaporating
(3) condensation and sublimation
(4) condensation and deposition | 2 | energy goes in |
18 Which transfer of energy occurs when ice cubes are placed in water that has a temperature of 45°C?
(1) Chemical energy is transferred from the ice to the water.
(2) Chemical energy is transferred from the water to the ice.
(3) Thermal energy is transferred from the ice to the water.
(4) Thermal energy is transferred from the water to the ice. | 4 | heat is thermal and goes from hot to cold |
19 At STP, 4 liters of O2 contains the same total number of molecules as
(1) 1 L of NH3 (3) 8 L of He
(2) 2 L of Cl2 (4) 4 L of CO2 | 4 | Avagodros Hypothesis-equal vol. of gas contain equal numbers of molecules |
20 What is the total number of electron pairs that are shared between the two carbon atoms in a molecule of ethyne?
(1) 1 (3) 3
(2) 2 (4) 4 | 3 | 3 there is a triple bond |